For the last decade, pyroelectric sensors have been used as the primary standard for UV dose calibration of excimer laser based lithography tools. At regular calibration intervals, the lithography tool is opened, the pyroelectric sensor is inserted onto the tool's wafer stage and dose measurements are taken. While these measurements are very useful as a calibration procedure, significant down time is created by opening the tool to insert the sensor.
In conventional immersion lithography processes, de-ionized (DI) water covers the gap between the projection lens of the lithography tool and the wafer. Because of even greater contamination concerns, opening the stage for dose calibration becomes even less desirable for immersion lithography.
U.S. Pat. No. 6,889,568, which issued on May 10, 2005, discloses a measuring device that incorporates a substrate with sensors that measure the processing conditions that a wafer may undergo during manufacturing. The substrate can be inserted into a processing chamber by a robot head and the measuring device can transmit the conditions in real time or store the conditions for subsequent analysis. In the measuring device disclosed in the '568 patent, the electronics platform is mounted on a recessed portion of the load bearing substrate.
U.S. Pat. No. 6,691,068, which issued on Feb. 10, 2004, discloses a sensor apparatus that is capable of being loaded into a process tool. From within the process tool, the sensor apparatus is capable of measuring, storing and transmitting data in near real time. As in the case of the '568 patent, in the apparatus disclosed in the '068 patent, the substrate is the load bearing foundation that carries the load of the sensor, the information processor and the power source.